Delayed arming device for mines



y 1951 L. E. KISSINGER 2,551,608

DELAYED ARMING DEVICE FOR MINES Filed NOV. 15, 1945 2 Sheets-Sheet l F 194 67 2 68 e9 e5 33 i2 7 8 79 1 45 48 as 64 34 37 r 44 29 33 i 7 A. r p4 35 v 83 42 36.

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22 24 23-- an ue/wtw L.EKESSZHQP May 8, 1951 L. E. KISSINGER 2,551,608

DELAYED ARMING DEVICE FOR MINES Filed Nov. 15, 1945 2 Sheets-Sheet 2 1vuvn'fom L. EKissinger abbowaq Patented May 8, 19 51 UNITED STATESPATENT UFFTE (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G.- 757) 8 Claims.

This invention relates to an electrolytic time delay device for arming amarine mine.

In the laying of mines from surface vessels or submarines it isnecessary that some means be provided for preventing the mine frombecoming armed until after the mine laying craft has removed to a safedistance. When only a few mines are being laid, as in a narrow channel,a delay of a few hours would be sufiicient. However, when extensiveoperations are being conducted and mines are being laid over a largefield, a time delay of as much as ten days may be desirable.

Heretofore various expedients have been employed to delay the arming ofa mine. The most common expedient has been to utilize a plunger which,when depressed, closes a circuit to start the arming or timing clock inoperation. The upper end of the plunger mounts a diaphragm which isexposed on its outer surface to the pressure of the sea water and underthe plunger there is placed a soluble washer. Such washers are usuallymade in the form of a salt cake impregnated with shellac. The washerdissolves in time and the plunger is thereby released and, being actedupon by the pressure of the sea water impinging upon the diaphragm, ismoved inwardly and.closes a switch to start the arming clock inoperation and arm the mine. Such devices are simple in construction andoperate very well but the time of operation is somewhat uncertain as itis difficult to predetermine the homogeneity of the washers and hencethe rate of dissolution of same, particularly when the washers are madeon a mass production basis and by semiskilled labor.

The object of the present invention is to provide an electrolytic minearming device which is certain in operation.

Another object of the present invention is to provide an electrolyticmine arming device which requires no positive acts on the'part of themine laying crew to initiate the operation of same.

A further object of the present invention is to provide an electrolyticmine arming device which has no electrolyte of its own but whichutilizes the ambient sea water for this purpose.

A still further object of the present invention is to provide anelectrolytic mine arming device which is capable of a predetermined timedelay in operation.

An additional object of the present invention is to provide anelectrolytic mine arming device which will necessitate little or nomodification of the conventional mine casing for incorporation therein.

Other objects, advantages, and improvements will become apparent fromthe following descrip- Fig. 4 is a top plan view of'the structure shownin Fig. 3, the retaining plate for the cathode plate being removed inthis view; and I i Fig. 5 is a view similar to Fig. 4 showing amodification in which the time delay resistor in the electrolytic cellcircuit is omitted, the'retaining plate for the cathode plate beinglikewise removed in this view.

Referring now to the drawings and to Figs. 1

and 2 in particular, there is here shown a con-' I0 having a hatch IItherein in which the arming or timing clock is" ventional mine casingmounted, this clock being designated by the reference numeral 20 appliedto the casing thereof.

A cylindrical wall I2 is mounted in the hatch hole and secured to themine casing Ill by a joint l3.

The hatch is closed at its bottom by a plate I4 which is secured to thecylindrical wall l2 by a joint l5. The bottom plate M has a central borel6 therethrough and a counterbore l1 extends from the lower face of theplate l4 approximately halfway through same; A hollow cylinder I8 ismounted in the counterbore I! in the" bottom plate l4, thiscylinder-abutting on-itsfi upper edge the bottom wall of thecount-erbore:-- The cylinder I8 is secured to the bottom plate I 45 by ajoint 19. Joints l3,l5 and [9 may be made" by brazing, soldering,welding, or the like.

A yoke 28 mounts the electrolytic cell and supports the arming or timingclock 20. yoke has an integral top plate 29 formed with a peripheral rim30 and an inwardly spaced annular raised rib 32. Circumferentiallyspaced and radially disposed reinforcing ribs 3| extend between theperipheral rim 3!] and the annular I rib 32 and are integral at theirrespective ends with same. place, circumferentially spaced holes 35 areformed in the ribs 3! and stud bolts 36 extend through these holes,these bolts being received at their lower ends in suitably threadedholes 39 in the bottom plate It. Nuts 37 and lock washers 38 are fittedon the upper ends of the stud bolts 36. The yoke gs has anintegraldepressed cen- This In order to secure the yoke 28 in testingbyinserting 'a rod-dike on the under face' of -theitop platetosecurethez:

gasket iniipla'cei. and increase the: contact areal The depressedcentral web 4!! merges with an integral centrally disposed hub 50 whichtermi-iimates in an integral radially extending flange 52 which in turnis integral with a downwardly" depending circumferential skirt 56,vthea1atter being of the proper diameter to have a tight" fit" in thecylinder I8. 54 and 55 are provided in the radially extending flange 52for a purpose which will appear here- Diametrically sp'acedi holeswinafter. The skirt 56 base a ricircumferentialc groove 51 therein forthe reception of 'a packing ring or gasket, not shown. On the top of thedepressed-"central=webr4ll thereis :iormed a concentrically-;disposedicircularx rib "-45. Arcuately spacedandx-radiallysidisposedreinforcing ribs .44 are integral at their inner endsfwith thecircularrib-.45 andfat their sbottoms and. outer ends with thedepressed. central:web-40: c A central bore 53" is =-formed::through=the fiange.r52 on. the central hub 50, a counterbore i throughi the-"central hub'i50, 1a 'counterb'ore' 49 =of increaseddiameter through the-depressed central -web'- lE3--,-- and 'a counterbore 4 46w-ofstillgreaterdiameterthrough- 1 the circular rib 45, the central bore 53, andthe r:

eounterbores 5 B14 9? and 4 providing :space" for therhydrostatemechanisms as: will be laterv described. The clookif! is securedrtothe-skirt r56 on the'uyoke 28-nby studubolts 159 =which extendthrough?suitable' holes 581 in-the flange1-52and;-: thee-skirt 56=f andihavewnuts 560- oneithervend, washers :5 I being disposedeunderethe nutsB5 on the upper ends of the stumboltsl iThai-arming"orvtimingEclockwZOis of the type generallyczdesc'ribed andillustrated" in the: co-

pendingiz-application of James :'B.: Glennon et -a1.,- Se'iial No.-395;230;'filed':May 26119415 for-Firing Mechanismfforza Submarine Mine.The casing ofttheaclock "is closed byfaa top platerZl through which'the'asupportingfboltstiiil extend '1. The bottorn" ofcthecclo'ckcasingizflltihassan 'integralE-boss 22 *form'edthereonfwherein':there:is mounted" a I transparentcinspectionx plate 1(not-i s-hown) which provides zforr viewingithe" .interior of the clockto determine theisequen'ce-s of the circuitfilosings forlrtwhich theclock def-arranged. 1 Also, forn'ied' oni the bottom of the casing ofthe-clock there is a second boss 23 through which'a cable 24 ex tends;this c'able 'carrying':thezcon'ductors to the" variouscomp'onentsi ofthe miner-arming"v andfir ing: circuits? A pluiiger 25"' extends throughthe when depressed", starts 1 the" clock*into= operation. A leaf springzl is 'securedwat'one' end by a screw 4 serting a screw driver throughthe hole 54 in the flange 52.

A plate 52 is positioned centrally of the top plate 29 of the yoke 28and this plate mounts the electrolytic arming cell 953. The plate 52 isformed with an" annulanrib "fifi on its-under f ace which rib fitswithin th'e rib-SE on the piate 29 when the plate 62 is in position. Theplate 62 is held in place by screws which pass through suitable holes inarcuate bosses 64. formed on the periphery "of 'the'plate, the screws 55being received'in suitable threaded holes 33 in arcuately spaced bosses34, which latter are integral with the aniiular rib'fi on" the plate 29.Suitable lock washershfifi are placed under the heads of the screws 55."A central raised boss 68 is formed on therplatecfiZ andra central holeit: through. the platez The bo'ss -iifi is provided with a counterbore6'! for the reception of the arming cell 98 andsthreads 59 :are: alsoprovided on the :exterior of the boss: -=-'Ihe threaded exterior V 69 ofthe bossprcvides for the reception of a protective cap (not shown) whichencloses the arming cell 51 duringvshipment and storage.-- A pluralityof arcuately spaced and radially positioned-holes l i is:provi-deotin'the plate '52 adjacent the annular" rib 53 for-theadmission'ofsea waterto the space'wbetween the-plate B2- and thedepressed central web 4!? on-the yoke '28;

The principal 5 component ofthe hydrostat: mechanism is aplunger'rl5'which passes'throughthe central hole 16 in the plate 62,the-counter bore 46- through'the circular rib 45; thecounterborefihthrough the centralhub 5t; and thecentral bore- 53 throughthe fiange 52 on the central hub:5El. -The p1unger l5'is threadedon itsupper endat Hand-a cotter key'l'3- passes through a diametral: hole (notshown) in the upper end of 15 4 1 with resp'ect to the leaf springs Acollar Hi-is "mounted around theaplung'er l5 and abuts the: plate'62 tolimit the upwardmovement of the plunger; The collar-His secured to theplunger IS-icy a radially positioned set screw "59. In order toaform thecollar :18 a female-pipe plug of suit able rdiameter may be reamed ofits threads; I A washer 86 is positioned around the lower-square"sectionrzll of :th'epluhger and abuts the shoulder l5 intermediate'thislsection andtthe'upper cylin'e' drical section of the plungerPositionedinter mediateth'e 'bottom'of the counterbore 5l=in the 26' tothe top' plaiteti I and' the other "end of 'this spring-overlies theplunger-25: When-the clockcasing 2 0 is attached to the skirt 56 cm theeen radially extending flaiige 52 on the'hub overlies the' springsecuringscrew ZB 'and' the hole 55 in this flahge overlies-the plunger-25? The arming cell 903 yoke -28,- -and" th clock 20"inay be removedbodily frdm the hatch! I 5 by unscrew ing the nuts3T fromthe'stud-bolts36 and, when sd:-'removed';'th' plunger 25 inay be depressed forinstrument tl'iibugh''"the"-holef55- in' the "flange 52;" likewise, thdeaf spring 21 r'naybe" removed-for changing th' tensi'o'n' of-same; orfor" replacement, by in-' nular'ridges il-being'providedon the bottom ofthis counterbore to secure the diaphragni against central 'hub'5ii andthe washerreil'thereis a coiled corripr'ession spring 8! which'biasestheplunger relationship, an enlarged convolution -84; 'concen tricallyformed'withvrespect to' the hole 83; this enlargied convolutio'nproviding for downward movement of the plunger 15." The diaphragm 82 isgripped at its central portion around the" hole 83 between a washer 85on the underside" oithcollarlfidrid the washer 85'. The periphery 'ofthe diaphragm 52 is secured on the bottom of-the counterbo're'45 inthecircular rib 45, an

creeping and increase the contact area. A ring nut 86 secures theperiphery of the diaphragm 82 in place, a washer 89 being interposedbetween the ring nut and the periphery of the diaphragm. The ring nut 85is secured in suitable threads 48 provided in the wall of thecounterbore 48 through the circular rib 45, the nut being provided withcooperating threads 88 on its periphery and with cross slots 8'! on itstop for the reception of a suitable wrench to facilitate insertion andremoval of the nut.

Referring now to Fig. 3, this figure shows the electrolytic arming cellin cross sectional view, the cell being designated generally by thereference numeral 90 applied to the casing thereof, and the cell beingmounted in the counterbore I51 in the boss 68 on the top plate 62. Thecasing 90 is in the shape of a ring orthimble With a central hole 9!therethrough. In the top face of the casing 90 there is formed ashoulder 92 concentrically positioned with respect to the hole 9|, thisshoulder forming a space for the reception of the cathode plate I02. Acover plate 95 is mounted on the top of the casing 90 by screws 93 whichproject through the cover plate and into suitablethreaded holes on thecasing 90.:

Washers 90 are interposed under the heads of the screws 93. The coverplate 95 has a central hole 96 therethrough, which registers with thecentral hole 9! in the casing 90 when the cover plate is in place, and aquadrant length arcuate slot 9! positioned radially intermediate thecentral hole BI and the periphery of the cover plate, for a purposewhich will appear hereinafter.

A grommet or washer I of hard rubber or other suitable material ismounted on the upper end of the plunger I5, this grommet having acentral bore 98 with internal threads 99 therein which threads cooperatewith the threads I2 on the upper end of the plunger 75. The grommet I00is secured against upward movement on the plunger I by the cotter key I3which, as previously stated, extends through a cliametral hole (notshown) in the plunger.

The cathode plate [0.2 is preferably made of pure zinc but may becomposed, if desired, of any metal suitable for the purpose such, forexample, as pure iron and has a central hole IiII which is received in asuitable groove in the grommet I00, a plurality of radially positionedand arcuately spaced holes I03 being provided in the oathode plate for apurpose which will appear hereinafter, and a connector lug I04 at onepoint on its periphery.

Formed in and extending downwardly from the top face of the casing 99there are two quadrant length arcuately shaped recesses I06 and I08,each having rounded ends. The adjacent ends of the recesses I05 and I08are connected by a restricted channel I01, this channel being formed byan outward extension I 99 of the inner wall of the recesses. A niche II0 is formed in the inner wall of the recess I06 adjacent the outermostend of the latter, the bottom of this niche constituting a shoulder II Iofiset from the inner wall of the recess I05, as shown in Fig. 3, andthis niche providing space for the connector lug I04 on the cathodeplate I02.

The anode of the electrolytic arming cell is formed by a silver cup H2of arcuate shape and with rounded ends and an open top, this cup beingpositioned in the arcuate recess I08 in the casing 90 and securedtherein by embedding in Wax I I3. The cup I I2 is filled with silverchloride II 4, this compound operating as a depolarizing 6 agent for theelectrolytic cell. In the modification of Fig. 4 a metal encasedresistor I I8 is positioned in the arcuate recess I06 in the casing andlikewise secured therein by embedding in the wax H3. A conductor H6extends through the restricted channel I0I between the arcuate recessesI06 and I08 and is connected at one end to the silver anode cup H2, asby soldering at I I5, and at the other end to the resistor I I8, againas by soldering at II I, this conductor likewise being embedded in theWax II 3. Similarly, a conductor H9 extends from the resistor H8 to theconnector lug I04 on the cathode plate I02, being secured thereto as bysoldering at I05, and this conductor is also embedded in the wax H3.

In the modification of Fig. 5, the resistor I I8 is omitted, theconductor H6 from the silver anode cup I I2 being connected directly tothe connector lug I04 on the cathode plate I02, again as by soldering atI05.

In assembly the cover plate secures the cathode plate I02 in placeagainst the shoulder 92 in the casing 90, this cover plate gripping thecathode plate beyond the outline of the holes I03 in the cathode plate.The arcuate slot 91 in the cover plate registers with the arcuate recessI08 in the upper face of the casing 90, thereby exposing the silverchloride I M in the anode silver cup II2 to the action of the sea water.

In operation, mines embodying the electrolytic arming cell of thepresent invention are planted in the usual manner from either surfacevessels, such as mine layers, or from submarines. While the electrolyticarming cell of the present invention can be used in mines dropped fromaircraft, its primary purpose is to provide a time delay in the armingof mines planted from surface vessels, or submarines, so as to permitthe laying vessels to safely come and go during several day of minelaying operations. When the mine is immersed in the sea Water the waterenters the space between the top plate 62 and the depressed central Web40 on the yoke 28 through the holes II in the said plate. The waterexerts pressure on the diaphragm 02 which pressure is resisted by thecoiled compression 8i but in addition the downward movement of theplunger I5 is prevented by the cathode plate I02 which is embedded inthe grommet I00 on the plunger I5 and secured between the cover plate 95and the casing 90 of the electrolytic arming cell. The sea water alsoenters the central hole 9! in the casing 90 of the electrolytic armingcell through the holes I03 in the cathode plate I02.

The sea water acts as an electrolyte for the arming cell andelectrolytic action sets in, the difference in potential beingapproximately one volt in the case of a zinc cathode or one-half volt ifan iron cathode is employed, and a current flows from the silver anodecup H2 to the cathode plate I02 through the conductor H6, resistor II 8,and the conductor H9, the cathode plate I02 being corroded away as thiselectrolytic action progresses. The electromotive force of the cellbeing fixed at approximately one-half volt or one volt, as the case maybe, the resistance of the conductors H6 and H9 being negligible, thecurrent flow will be determined largely by the value of the resistor H8,the maximum value of current flow being attained in the modification ofFig. 5 where the resistor I I8 is omitted and the silver anode cup H2 isshorted directly to the iron cathode plate I02 through the conductor H6.At some stage during the electrolytic action and the resultant corrosionawaybfthe cath'ode 'plate' "1 52 the plate will be fraptured and'thediaphragm 2and the'plunger act-'on zboth sides of the cathode plate,also function-lto reduce theeffectivearea of the cathode plate an'd theamount of the' plate to' becorroded away before the latter will befractured.

Although the invention has been described and illustratedfasa delayedarmingdevice for mines, it is obviously'cap'able of other uses, suchgiorinstance, as a sterilizingdevice' for depth charges and: torpedoes.

While there is'here shown and described a certain :preferred "embodimentof the invention,

many other' and varied forms and uses will: present themselves to thoseversed in the art without' departing from the spirit of 'the' invention,

and the invention; therefore'is not limited instructure or in'use exceptas indicated by the terms and scope of the appended claims.

The' invention herein "described and claimed may" be manufactured andusedby 'or for the Government of theUnitedStates' of America for'governmental purposes without the payment of any royalties thereon ortherefor.

What is claimed as new and "desired 'to be secured byLetters'Patent ofthe United States is:

l.' In a marine mine having 'an' arming clock therein; a movable memberadapted to start the" clock" into operation, an electrolyticarmin'g cellmounted in the mine casing; said electrolytic cell comprising acasing'with an aperture therein, an anode element mounted in a recess insaid cell casing and exposed to the ambient sea Water; a plate-' likecathode element mounted in the "cell casing and secured thereto, acircuit connection between theanode and cathode'elements, a cover platesecuring said cathodeelement in'position and havmg an apertureregistering'with' the aperture in the cell casing anda second apertureregistering with said anode element, a joint'member centrally mounted insaid cathode element, said cathode element having a row of holesintermediate the firstnamed aperture in said cover plate and thejoint'member, the coverplate, said row of holes, and'th'e jointmemberreducing the area of the cathode elementexposedto the seawater, a biasedmember connected by the jointmemb'er tothe cathode element andinitially'restrained by the cathode element against movement withrespect to the" cell Casing/said biased member being arranged tomove'the clock starting member'to a clock starting position when-thebiased member is moved against the bias thereon, and

means responsive to th'e pressure of the sea water for moving saidbiased member to the clock'starting position when said cathode elementis weakened sufliciently by electrolytic action and the sea pressureexceeds said bias.

2. In a mechanism of the character disclosed it Ithereon being shown indotted val of timeafterthe mine is submerged withina body of water, thecombination *of a' clock" arrangedwithin said mine forarming the mineapredetermined 'interval'of time after the-clock-isset in operation;- a'movablemember for setting said "CIOCR' in operation when 'said memberis moved from an initialpositionto a moved -posi tionya biasing memberfor yieldablyurging saidmovable member insaid initialposition, anormally inactive electrolytic cell includinga cathode element and ananode elementelectrically co nected togetherysaid'cell beingconstructed-and arrangedto become activated when wateri 'ad' mittedtherein thereby causing saidcathode-element to corrode away apredetermined interval of -time'after saidcell becomes activated, meansfor admitting water within said cell as-the mineis submerged within abody of water, means in eluding said-cathode element for releasablylocking said movable member in said initial position until saidcathodeelement has corroded away, and pressure responsive means arranged-in'=com'-- munication with the "surrounding --water whenthe -mine-issubmergedtherein'for moving said movable member from" said initialposition-tosaid moved position when a predetermined pres- I sure'i'applied to said pressure responsive means" and" when said cathodeelement has corroded:

away.

3. Ina marine mine having anarming c1ock-- therein ior-armingthe minea-predeterminedinterval of time 'after'the-clockhas been setin'operation, the'combination ofa first movable member for setting saidclock in 'operationwhem saidfir'stmember is moved 'from an initialposition to a'move'd position, a biasing -member foryieldably urgingsaid 'first'member'toward said" initial position, an electrolytic cellincluding a said initial position to said moved position when the waterpressure on the second memberreac'hes' a predetermined value sufiicientto overcome the opposing force of said biasing member and when saidcathode element has corroded away 'sufficiently to release said secondmember? 4. In a marine mine having an arming clock therein forarming themine a predetermined interval of time after the'clockhas been set inoperation, the combination of a movable member for setting the clock inoperation when the mem-' be is moved from an initial'position to a movedposition, a spring for yieldably urging said movable member into saidinitialposition, an'elec trclytic cell including a cathodeelementreleasably connected to said'mova'bl'e member-and an anode element arrangedwithin the cell, a circuit for connecting said cathode" element and saidanode element together whereby 'a current-is caused to flow between saidelements when water is admitted theretowithin said cell, means'for'admitting waterwithin-saidelectrolytic cell when the mine issubmergedtherein for causing said for arm'ing a marine mine a predetermined intercathode element to corrode away a predeternqinecl' length of time aftercurrent is caused to flow between said cathode element and said anodeelement, means including said cathode element for releasably lockingsaid movable member in said initial position until the cathode elementhas corroded away by electrolytic action sufficiently to release themovable member therefrom, a resistance included in said circulit forlimiting said current flow to a predetermined value suflicient to causesaid cathode to release the movable member a predetermined interval oftime after the current is caused to flow, and pressure responsive meansarranged for communication with the surrounding water when the mine issubmerged therein for moving said movable member from said initialposition to said moved position when the movable member is released andthe water pressure on said pressure responsive means reaches apredetermined value.

5. A mechanism for arming a marine mine comprising, in combination, anarming clock disposed Within said mine for arming the mine apredetermined interval of time after the clock has been set inoperation, a lever for starting said clock in operation when the leveris, moved from an initial position to a moved position, an electrolyticcell including an anode element and a cathode element arranged forcommunication with the surrounding water when the mine is immersedtherein, said cathode element being connected to said lever therebyforming a latch for releasably maintaining the lever in said initialposition thereof, a circuit forming a connection between said anode andcathode elements and adapted to cause a predetermined current to flowtherebetween in response to the electrolytic action of the sea waterthereon, said predetermined current flow being sufiicient to cause saidcathode element to corrode away to release said lever a predeterminedperiod of time after the mine is submerged, and means responsive to apredetermined degree of pressure of the said water for moving said leverfrom said initial position to said moved position when said cathodeelement has corroded to release the lever.

6. In a marine mine having a clock therein for arming the mine apredetermined period of time after the clock is set in operation, thecombination of an electrolytic cell including a cathode element and ananode element arranged for communication with the surrounding water whenthe mine is submerged therein, a circuit for causing a current flowbetween said cathode element and anode element when the mine issubmerged whereby the cathode element is caused to corrode away byelectrolytic action thereon a predetermined length of time after saidcurrent flow is started, a lever releasably locked to said cathodeelement prior to said corroding away thereof and arranged to be moved bypressure of the surrounding water when the mine is submerged and thelever is released from said cathode element,

said lever being constructed and arranged to set the clock in operationas the lever is moved by said water pressure from an initial position toa moved position, a spring for yieldably urging said lever toward saidinitial position whereby said lever is moved to said moved position whenthe Water pressure on said lever reaches a predetermined value.

7. An arming circuit for a marine mine comprising a circuit controllingmeans including an arming clock for arming said circuit a predeterminedlength of time after the clock has been set in operation, a lever forstarting said clock in operation when the lever is moved from an initialposition to a moved position, means for yieldably urging said lever intosaid initial position, an electrolytic cell including an anode elementand a cathode element arranged for communication with the surroundingwater when the mine is submerged therein, said cathode element beingconstructed and arranged to releasably maintain said lever in theinitial position, a circuit including said anode element and cathodeelement for causing said cathode element to corrode away to release saidlever a predetermined periodof time after the mine is submerged, andmeans respon sive to a predetermined degree of pressure of thesurrounding water for moving said lever from said initial position tothe moved position when said cathode element has corroded to releasesaid lever.

8. In an electrolytic device of the character disclosed, the combinationof an electrolytic cell including an anode and a cathode electricallyconnected thereto, a non-conducting casing for the cell, a movableelement initially secured to a first portion of the cathode, means forsecuring a second portion of the cathode tothe casing, means foradmitting sea water to said anode and to a third portion of the cathodeintermediate said first and second portions when said device is immersedwithin the Water thereby to initiate corroding of said intermediatecathode portion by electrolytic action of the sea water thereon, saidelement being locked by the cathode in an initial position to saidcasing until said intermediate cathode portion has corroded sufficientlyto sever said first and second cathode portions thereby to release theelement for movement with respect to the casing, and means responsive topressure of the surrounding water for moving the element upon releasethereof.

LEWIS E. KISSINGER.

REFERENCES CITED UNITED STATES PATENTS Name Date Leon Feb. 23, 1909Number

